Programming

The Programming Process

Basic Computer Components

Programming Languages

Problem Solving

Case Study - Payroll Program

Programming

• Programming - scheduling, or performing a task or and event.
  
  
  
• Computer Programming - creating a sequence of steps for a computer to follow in performing a task.
  
  
  
• Programming Language - a set of rules, symbols, and special words used to construct a computer program.
  
  
  
• Programming language rules consist of:
  
  
  
• Rules of Syntax which specify how valid instructions are written in the language.
  
  
  
• Rules of Semantics which determine the meaning of the instructions (what the computer will do).
  
  
  
• Computer programs range in size from very small (like the ones we will create in this class) to extremely large (like Windows 98, etc.).
  
  
  
• Comparison of small and large programs:
  
  

The Programming Process

• Programming can be viewed as a three phase process:
  
  

• An Algorithm is a step-by-step procedure for solving a problem in a finite amount of time.

•  Problem Solving Phase

 

Analysis and Specification. Understand (define) the problem and what the solution must do.  General solution (algorithm). Develop a logical sequence of steps to be used to solve the problem.  Verify. Follow the steps exactly to see if the solution really does solve the problem

 
• Implementation Phase

 
 

 

Concrete Solution (Program) Translate the algorithm into a programming language.  Test. Have the computer follow the instructions, manually checking the results. If errors are found, analyze the program and the algorithm to determine the source of the errors, then make corrections.

 

• Maintenance Phase

 

Use. The program is distributed and used by one or more individuals.  Maintain. Modify the program to meet changing requirements or to correct any errors that show up in using it.

 

Basic Computer Components

• Computer block diagram:

• Central Processing Unit (CPU) - The part of the computer that executes the instructions (program) stored in memory. The CPU is made up of the Control Unit and the Arithmetic/Logical Unit.
  
  
  
• Control Unit - The component of the CPU that controls the actions of the other components so that instructions are executed in the correct sequence.
  
  
  
• Arithmetic/Logical Unit (ALU) - the component of the CPU that performs arithmetic and logical operations.
  
  
  
• Memory Unit - Internal data storage in a computer. The memory is comprised of a large number of individual cells, each with a unique number, known as its address, associated with it.
  
  
  
• Each memory cell is made up of a set number of binary digits (bits).
  
  
  
• A Bit is can store one of two values, denoted by a 1 or 0.
  
  
  
• The Memory Unit stores several different types of data:
  
  
  
1. Numbers - integers, reals, etc.
   
   
   
2. Characters - alphabetic, punctuation, special symbols.
   
   
   
3. Logical data - True/False results.
   
   
   
4. Instructions - Program data that instructs the computer as to what to do.
   
   
   
• A computer's memory is volatile - its contents are lost when power is turned off.
  
  
  
• Peripheral Devices - Equipment attached to a computer.
  
  
  
1. Input Devices - Instruments for entering data into a computer.
• Keyboard
• Mouse
• Microphone
• Scanners
• CD-ROM Drive
  
  
  
2. Output Devices - Components for displaying or presenting data to users.
• Monitor
• Printer
• Speaker
• CD-ROM Burner
  
  
  
3. Storage Devices - Components for long-term storage of data.
• Floppy Disk
• Hard Disk
• Rewritable Optical Disk

Programming Languages

• Programming Language - a set of rules, symbols, and special words used to construct a computer program.
  
  
  
• Machine Language - the binary representation of the instructions that a computer's hardware can perform.
  
  
  
• Assembly Language - a low-level programming language in which a mnemonic is used to represent each of the machine language instructions for a specific computer.
  
  

• Assembly language programs also allow the user to use text names for data rather than having to remember their memory addresses.
  
  
  
• An Assembler is a computer program that translates an assembly language program into machine code.

• Source Program - A program written in a human readable version.
  
  
  
• Object Program - The machine language version of a source program.
  
  
  
• High-Level Language - A computer language that is more understandable and closer to standard notations than assembler language.
  
  
  
• C++ is a high-level language based on algebraic notation.

• Compiler - a computer program that translates a high-level language to an object program.

Problem Solving

• Computer programs are very complex. Creating large programs may include making millions of individual decisions.
  
  
  
• Solving such complex problems requires a disciplined approach.
  
  
  
• The only effective way to create complex programs is to break the problem into smaller subproblems and repeating the processing until only simple problems are left.

Case Study - Payroll Program

• The description of a simple company payroll program can be found on pages 32-34 of the text.
  
  
  
• Payroll C++ Program.